BIMETALLIC WEAR LINER AND ITS PREPARATION METHOD

Description

TECHNICAL FIELD

The present disclosure relates to the field of bimetallic composite casting technology, particularly a bimetallic wear liner and its preparation method.

BACKGROUND

The wear liner of a crushing device is classified as a wear-resistant wear part, and its service life and replacement frequency directly determine the working efficiency and product cost of the crusher. While single material wear liners, such as high manganese steel and high chromium cast iron, may have low purchase costs, they have high operating costs. High manganese steel exhibits good toughness, but is not resistant to friction and wear. It is suitable for workplaces with a large impact. Under the action of impact force, austenite is transformed into martensite, which improves wear resistance. High chromium cast iron exhibits high hardness but high brittleness, making it suitable for workplaces with large friction and wear. For crushing conditions with impact and wear, bimetallic composite liners are commonly utilized, which combine low alloy steel with good toughness and high chromium cast iron with high hardness, it balances the conflicting properties of toughness and wear resistance.

In the prior art, there are many composite methods of producing bimetallic composite liners, such as casting, surfacing, explosive welding, plating, plasma spraying, etc. Among these, casting is the most economical method, particularly suitable for workpieces with thick wear layers. However, for plate-shaped castings, it is difficult to compound bimetallic metallurgy due to its shape and size constraints, and many invention patents on plate-shaped castings have the problem of low operability. For example, an invention patent application with publication number CN101357398A discloses a production process method for a double-liquid bimetallic composite casting jaw plate. Two gating systems are adopted: firstly, high chromium cast iron is poured, secondly, low alloy steel is poured in a shower mode after an interval of time. In this method, severe oxidation of molten steel will be caused, making it difficult to ensure the casting quality and properties of low alloy steel. Patent publication number CN1039204C discloses a method for casting a jaw plate by using liquid high chromium cast iron and cast steel composite. Similarly, the high chromium cast iron is poured first, secondly, the cast steel is poured after solidification. In this method, the temperature distribution or uniformity of the composite surface of plate-shaped members is not considered. The patent with publication number CN104174833B discloses a production process for a double-liquid bimetallic composite casting wear thin plate, with a double gating system, and a special chilling material to adjust the temperature field of the molten metal in the cavity, so that the temperature gradient of the contact part between the molten metal and the chilling material is large, while the temperature gradient is relatively small in the distant regions; when the large part of the low alloy steel has formed a solid phase and the surface of the small part of the low alloy steel has a solid-liquid or liquid phase, the high chromium cast iron molten is poured into the remaining space of the cavity, and the two molten metals achieve metallurgical bonding without mixing. Nevertheless, the thickness of the low alloy steel layer in the first time of pouring cannot be precisely controlled by this process. The patent application with publication number CN115870480A discloses a manufacturing process for a double-liquid bimetallic composite casting jaw plate, the chill is arranged at the bottom, the high chromium cast iron is poured in the cavities of a drag and a transition cope, the transition cope is dismantled, the cope is closed, and then the molten steel is poured. In the process, the operation of dismantling and reassembling boxes must be performed at short intervals, which is labor-intensive. The patent with publication number CN111195711B discloses a bimetallic composite method for gyratory crusher liner, by using the same gating system to pour molten steel and molten iron in turn, and the pouring height and temperature of the carbon steel layer are determined through observation holes. The first limitation is that a single gating system, high chromium cast iron is easy to intermix with the carbon steel in the gating system during pouring, leading to changes in the composition of the high chromium cast iron. The second limitation is the reliance on artificial experience factors, so the product quality is unstable and not suitable for large-scale industrial production.

Consequently, in order to obtain high-quality bimetallic metallurgical composite wear liner, it is necessary to put in time and energy not only on the molten metal smelting and gating system, but also on the interface of metallurgical composite, such as improving the smelting quality of high chromium cast iron to enhance its toughness, using overflow port to ensure the thickness of base layer, purifying the interface of metallurgical composite to avoid oxidation, and controlling the cooling rate to control the consistency of interface temperature. The patent with publication number CN117483722B discloses a manufacturing method for a bimetallic wear thin plate, which adopts a wing edge cavity to slow down the heat dissipation around molten metal, and uses chill to strengthen unidirectional heat transfer to make the temperature of the interface uniform. The outer side of the wing edge cavity is communicated with an overflow port to control the pouring thickness of the base layer. A protective gas is introduced into the cavity to prevent the molten steel from being oxidized during the shower pouring, and to purify the interface. The interval time is simulated by a computer, and the simulated temperature of the interface is the temperature of the solid-liquid two-phase region. However, when the base layer solidifies, it is impossible for the molten metal of the wear layer to re-melt the base layer to produce a metallurgical composite, and it can only produce a metallurgical composite when the base layer is in a semi-solidified state (coexistence of solid and liquid phases) or liquid state. If the upper surface of the base molten metal, that is, the interface, remains in a liquid state, it will cause over-melting.

Additionally, the metallurgical composite in patent publication number CN117483722B refers to the composite of a liquid state and a liquid state, that is, there is a process in which as-cast crystals grow from the base layer to the wear layer, and does not include the metallurgical composite caused by atomic diffusion. With the increase in the thickness of the wear liner, the rapid cooling ability of the chill decreases with the increase in its heating temperature, the difficulty of unidirectional solidification control of the wear liner gradually increases, and the uniformity of the interface becomes worse. Particularly when the protective gas is introduced, once the interface is solidified, it is impossible to perform the feeding on the base layer, which makes the base layer produce shrinkage defects and become waste products. Consequently, there is a requirement to improve the aforementioned methods to yield a production process for a bimetallic wear liner with a thicker thickness.

SUMMARY

An objective of the present disclosure is to provide a bimetallic wear liner and its preparation method. The molten steel in a slag collecting tank is used to avoid heat dissipation around a base layer, and the molten steel in the base layer undergoes bidirectional heat dissipation. The interface retains local high temperature as a feeding channel of the base steel. In the pouring process, the cavity isolates air, to avoid oxidation, and purify the interface, and a metallurgical composite is obtained.

In order to achieve the above objective, the present disclosure provides a preparation method for a bimetallic wear liner, the method includes the following steps:

• • S1, molten metal melting: using high chromium cast iron as a wear layer, using low alloy steel as a base layer, and melting the high chromium cast iron and the low alloy steel respectively by two intermediate frequency furnaces, thereby obtaining molten iron of high chromium cast iron and molten steel of low alloy steel;
  • S2, modeling: using a molding flask formed by combining a cope and a drag, where a cavity is arranged between the cope and the drag, the molding flask is provided with independent iron runners and steel runners to ensure their respective pouring components, to avoid using one runner that results in mutual melting and affects the composition of high chromium cast iron. A parting line of the molding flask is a bimetallic metallurgical composite interface, an inner gate of the steel runner is arranged on the parting line of the drag, an inner gate of the iron runner is arranged on the parting line of the cope, the parting line of the cope is provided with an overflow port, the overflow port is communicated with a slag collecting tank, and a plurality of the overflow ports are respectively arranged on an opposite side of the inner gate of the iron runner and an opposite side of the inner gate of the steel runner for controlling a pouring thickness of the low alloy steel, thereby ensuring uniform thickness dimensions of the base layer of the liner. The slag collecting tank is arranged inside the molding flask. Volume of the slag collecting tank under the parting line is larger than volume of the steel runner above the parting line, so as to ensure that the overflow port is still smooth after the molten steel of the low alloy steel is stopped pouring, and the interface is a lower plane of the overflow port. The slag collecting tank collects low-temperature oxidized molten steel at a front end of the molten steel of low alloy steel pouring, a heat dissipation thermal resistance around the base layer is increased by using the molten steel, and further collects low-temperature molten iron wrapped with oxidized slag at a front end when the high chromium cast iron is poured, so as to achieve an objective of pure interface and consistent interface temperature. A blind riser is arranged inside the molding flask above the cavity. The drag is provided with a steel mesh at a position 1-3 mm away from the parting line, and a main objective is to rapidly form a solid barrier at the interface to avoid mixing of molten iron and molten steel.
  • S3, pouring: covering an opening of the cavity communicating to outside with an organic film, firstly, pouring the molten steel of low alloy steel obtained in S1 into the cavity along the steel runner, with a pouring temperature of 1541° C.-1555° C., pouring the molten iron of high chromium cast iron obtained in S1 into the cavity along the iron runner after an interval of time, with a pouring temperature of 1486° C.-1500° C., controlling a temperature difference of the pouring temperature within 15° C., thereby obtaining a liner.

In some embodiments, high chromium cast iron is melted by using furnace raw materials with a low phosphorus content or an industrial pure alloy, molten iron is melted to make reducing slag, then alloyed, and high-temperature steel slag is mixed into an iron ladle after rapid heating. Inert gas is introduced into the molten iron through a porous plug at the ladle bottom, the molten iron is stirred to promote contact between the molten iron and the reducing slag, and a desulfurization and deoxygenation reaction is strengthened. Meanwhile, an alloy wire is fed to the iron ladle for a wire feeding treatment for modification and inoculation. The gas is closed, the slag is removed, and a slag collecting insulation agent is covered, and the ladle is transferred to the molding flask to stand for pouring. The modification and inoculation treatment and reducing slag gas purging refining technology of high chromium cast iron belongs to the prior art and aims to improve the toughness of high chromium cast iron from by reducing inclusions and refining grains.

Low alloy steel is melted using low-phosphorus scrap steel and low-phosphorus alloy. After molten steel is melted, reducing slag is made. A deoxidizer in the furnace is a silicon-calcium-barium alloy. Barium and calcium can significantly improve a morphology of inclusions and turn long inclusions into fine spherical inclusions, which is conducive to improving the toughness of low alloy steel. After the temperature is raised for 4-5 min, the high-temperature steel slag is mixed into a steel ladle. The mixing of steel slag increases the contact reaction interface between reducing slag and molten steel, and promotes the desulfurization and deoxidation reaction. A rare earth magnesium ferro-silicon alloy is pre-placed at the bottom of the steel ladle, and the rare earth magnesium ferro-silicon alloy is used to deoxidize the ladle. In addition to inclusions formed by deoxidation and desulfurization of rare earth elements added to molten steel, the remaining amount will also dissolve in molten steel and perform an equilibrium distribution of solutes at the growing solid-liquid interface, resulting in enrichment on a liquid phase side at a front of the solid-liquid interface, a solute equilibrium partition coefficient K value of Mn and other elements can be increased, and a segregation can be reduced. Additionally, the addition of Mg, Ca, Ba and other elements can promote the purification of inclusions, because both Mg and Ca have strong activity and can desulfurize and deoxidize themselves. Particularly, the addition of Mg further promotes the spheroidization of inclusions. The joint action is conducive to increasing the amount of solid soluble rare earths in steel, and further giving full play to the purification effect of rare earths.

In some embodiments, in S1, the high chromium cast iron includes the following components in percentage by mass:

• • 2.6%-2.8% of C, ≤1% of Si, 0.6%-1.2% of Mn, 25%-27% of Cr, 0.4%-0.6% of Mo, 0.2%-0.4% of Ni, with the balance being Fe and unavoidable impurities; in S1, when the low alloy steel is melted, the deoxidizer in the furnace adopts the silicon-calcium-barium alloy, and the addition amount of the silicon-calcium-barium alloy is 0.35%-0.45% of the mass fraction of the molten steel in the furnace;
  • the deoxidizer in the steel ladle adopts the rare earth magnesium ferro-silicon alloy with a size of 3-8 mm, and an addition amount of the rare earth magnesium ferro-silicon alloy is 0.30-0.35% of the mass fraction of the molten steel in the ladle;
  • the silicon-calcium-barium alloy includes the following components in mass fraction:
  • 38.55%-42.69% of Si, 6.60%-7.26% of Ba, 18.17%-19.93% of Ca, with the balance being Fe and trace amounts of other impurities;
  • the rare earth magnesium ferro-silicon alloy includes the following components in mass fraction:
  • 6.17%-7.82% of RE, 7.05%-8.76% of Mg, 35.88%-43.14% of Si, ≤1.0% of Ti, ≤1.0% of Al, with the balance being Fe and trace amounts of other impurities.
  • 0.35%-0.45% of silicon-calcium-barium alloy and 0.30%-0.35% of rare earth magnesium ferro-silicon alloy are added into the low alloy steel, contributing to promoting a significant refinement of a solidification structure, a significant reduction of inclusion quantity and a spheroidization of inclusion morphology, and significantly improving plasticity and toughness of low alloy steel.

In some embodiments, in S2, an internal chill is arranged inside the cavity, the internal chill is a column-base structure, and a top end of the internal chill is provided with a groove.

In some embodiments, in S2, the surface of the steel mesh is provided with a void, the void is located below the blind riser, an objective of the arrangement of the void is to have a solid-liquid two-phase temperature or a liquid-phase temperature locally at the interface, and the void is used to become a feeding channel of the low alloy steel when the molten iron of high chromium cast iron is poured, and in combination with the blind riser, to increase direct vertical pressure of the feeding of the low alloy steel.

In some embodiments, in S2, an observation port is arranged above the molding flask, and the observation port is located on an opposite side of the steel runner and directly above the slag collecting tank. Weight control can be adopted for the low alloy steel pouring. The weight displayed on an electronic scale lags behind the pouring weight. The difference between the two weights depends on the pouring speed. If the requirements on cost or pouring quality are strict, it is convenient to observe the pouring situation of molten steel through the observation port. By using the slag collecting tank to adapt to the fluctuation of molten steel pouring weight and controlling the thickness, the thickness of the molten steel in the base layer can still be guaranteed.

In some embodiments, in S2, an external chill is arranged below the molding flask, an upper surface shape of the external chill is the same as a bottom surface shape of the base layer, a lower surface of the external chill is a spherical surface, and a thickness dimension of the external chill on a side close to the steel runner is larger than other side dimensions of the external chill. The function is for rapid uniform unidirectional solidification.

In some embodiments, after S3, a tempering treatment is performed on the liner to obtain a bimetallic liner with no shrinkage in the base layer and metallurgical composite at the interface.

In some embodiments, the tempering treatment is:

• • the liner is heated to 1050-1080° C. with the furnace, held for 60-80 min to achieve a high temperature uniform diffusion and reduction of casting segregation, then furnace-cooled to 980-1000° C., soaked for 80-90 min, and then removed from the furnace, the high chromium cast iron side of the liner is spray quenched, with the cooling rate of the spray quenching controlled at 25-32° C./s, when the surface temperature of the low alloy steel side of the bimetallic liner drops below 250° C., it is transferred into a heat treatment furnace at 200° C.-250° C. for tempering for 5-8 h, followed by air cooling to room temperature after removal from the furnace.

The principle of spray quenching is to spray water and air as a mist mixture onto the surface of the workpiece, achieving rapid cooling through the contact between the mist droplets and the workpiece. This process includes four key heat transfer stages: stable film boiling, transitional boiling, nucleation boiling and natural convection heat transfer. By optimizing heat transfer at these stages, the cooling efficiency can be significantly improved. The cooling rate of spray quenching mainly depends on the spray density of the cooling medium, that is, the mass flow rate of coolant per unit time and unit area. Spray quenching can avoid the generation of steam film during general hydrostatic quenching, thereby improving the cooling capacity and increasing the depth of the hardened layer, ensuring that the parts that do not need hardening are not quenched, and the tendency of quenching cracking is also small. The hardness and wear resistance of the high chromium cast iron can be improved by only spray quenching the high chromium cast iron side of the liner. The low alloy steel side of the liner is naturally cooled without the spray quenching treatment, which is equivalent to normalizing treatment. After cooling, fine pearlite is obtained, so that the low alloy steel side exhibits high strength and toughness. When the surface temperature of the low alloy steel side is cooled to below 250° C., the high chromium cast iron has been quenched, and the internal temperature of the low alloy steel base layer is slightly higher, so the liner is immediately sent to the heat treatment furnace for stress relief treatment to stabilize the structure.

In some embodiments, in S3, the opening of the cavity communicating with the outside includes the iron runner, the steel runner, and the observation port.

In some embodiments, the molten steel of low alloy steel is covered with organic film before pouring, so that the cavity and the outside air passage are completely covered, and the air in the cavity can overflow, but the outside air cannot enter the cavity, so as to reduce the oxidation of the molten steel and purify the interface. In order to prevent molten steel from splashing and scalding the organic film, the organic film can be covered with a sand layer, and the organic film at the pouring port and observation port should be covered with refractory wool to facilitate operation.

In some embodiments, in S3, the temperature difference of pouring temperature is controlled within 15° C. When pouring low alloy steel, it is to obtain the same interval time. That is, by controlling the pouring temperature and utilizing the steel mesh, in the same interval time, the temperature at the low alloy steel interface can be maintained within the ideal range for molten iron of high chromium cast iron pouring, specifically, at its solidus temperature. The interval time is the time from the pouring of molten steel of low alloy steel to the pouring of molten iron of high chromium cast iron. The interval time is based on the time of the computer simulation and actual pouring verification. The time can not be changed arbitrarily after determination. Only in the case of large changes in the boundary conditions of the simulation, such as sand changes, steel mesh changes, etc., adjustments may only be made under the guidance of technical personnel. This control avoids the influence of the human factors of the operator. When pouring high chromium cast iron, it is necessary to strictly control the quality of the bimetallic metallurgical composite interface and avoid low temperature non-melting or high temperature over-melting. Because the interval time has been determined, it is easy to control the pouring temperature of molten iron of high chromium cast iron alone, which is convenient for the pouring operation.

In some embodiments, when the molten steel of low alloy steel is poured, the filling state of the molten steel is observed through the observation port, when the overflow port is bright, the pouring is stopped, the molten steel in the runner continues to be filled under the action of gravity, and the excess molten steel in the cavity flows into the slag collecting tank from the overflow port. Alternatively, pouring weight control is employed instead of using the observation port. After the molten steel of low alloy steel is stabilized, the overflow port should be kept smooth, and the inner cavity of the slag collecting tank below the parting line should not be filled. After an interval of time, the molten iron of high chromium cast iron is poured. The molten iron of high chromium cast iron flushes part of the oxide slag on the interface into the slag collecting tank, and part of the oxide slag flows into the blind riser with the molten steel. The flowing molten iron of high chromium cast iron purifies the interface, and the temperature tends to be consistent, which provides the basis for metallurgical bonding.

The interface of the solid low alloy steel and the high-temperature molten iron of high chromium cast iron is diffused or liquid-liquid fused to form metallurgical bonding. The part of the interface with voids provided a feeding channel for the molten steel of low alloy steel. The molten iron of high chromium cast iron fed the shrinkage in the low alloy steel, to avoid shrinkage defects in the low alloy steel.

The present disclosure further provides a bimetallic wear liner.

Therefore, the present disclosure adopts the bimetallic wear liner and its preparation method, and has the following beneficial effects:

(1) The present disclosure has good process operability and a high product qualification rate. In the aspect of shaping, the organic film is adopted to block and isolate the air outside the cavity, the cavity isolates the air, the oxidation of molten steel on the interface is avoided, the interface is purified, and the interval time is fixed, so that the process operability is improved, to control the cooling speed of molten steel, then the temperature and uniformity of the interface are controlled, the pouring temperature is controlled in a narrow range, and the product quality is guaranteed, thereby obtaining the bimetallic wear liner with good metallurgical bonding. In the aspect of heat treatment, the high chromium cast iron side is spray quenched, and the low alloy steel side is naturally cooled and normalized, and the expected performance is obtained at different cooling rates. The heat treatment operation is convenient and feasible, and the product performance is excellent.

(2) In the present disclosure, the slag collecting tank is used to collect low-temperature molten steel and low-temperature molten iron with oxidized slag at the front end, the molten steel avoids heat dissipation around the base layer, the molten steel in the base layer is bidirectional heat dissipation, and the interface surface retains local high temperature as a feeding channel for the molten steel in the base layer. In order to obtain a good metallurgical composite and ensure the compactness of the base layer (without shrinkage), the slag collecting tanks on both sides and the runners on both sides greatly increase the thermal resistance of heat dissipation around the low alloy steel, strengthen the heat dissipation in the direction of plate thickness, and then the interface with uniform temperature is obtained.

(3) In the present disclosure, the steel mesh is used to produce a high-temperature interlayer, to avoid the mixing of molten iron and molten steel, ensure the stable control of the composition of the high chromium cast iron, and further obtain the stable performance of the wear layer. Moreover, the high-temperature solid state is beneficial to atomic diffusion and liquid mutual melting into metallurgical bonding. The void becomes the feeding channel of molten steel, the thicker base layer has no shrinkage defects, and the bimetallic composition is well controlled to ensure the stability of the performance of the wear layer.

Further detailed descriptions of the technical scheme of the present disclosure can be found in the accompanying drawings and embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a molding flask structure of a bimetallic wear liner and its preparation method according to Example 1 of the present disclosure;

FIG. 2 is a top view of a bimetallic wear liner and its preparation method according to Example 1 of the present disclosure;

FIG. 3 is a side view of an embodiment of a bimetallic wear liner and its preparation method according to Example 1 of the present disclosure;

FIG. 4 is a schematic diagram of a molding flask structure of a bimetallic wear liner and its preparation method according to Example 2 of the present disclosure;

FIG. 5 is a microscopic view of a bimetallic wear liner and its preparation method according to Example 3 of the present disclosure, wherein (a) is a base layer, and (b) is a wear layer;

FIG. 6 is an interface microscope view of a bimetallic wear liner and its preparation method according to example 3 of the present disclosure.

REFERENCE NUMERALS IN FIGURES

• • 1, a steel runner; 2, a blind riser; 3, an iron runner; 4, an observation port; 5, a slag collecting tank; 6, an overflow port; 7, a steel mesh; 8, an external chill; 9, a void; 10, an internal chill.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical scheme of the present disclosure is further explained below by drawings and embodiments.

Unless otherwise defined, the technical or scientific terms used in the present disclosure shall be those to which the present disclosure belongs.

Example 1

The example is suitable for a bimetallic wear liner with a base layer thickness of more than 30 mm, and the bimetallic wear liner has a replacement cycle. In order to achieve that the wear liners with different thicknesses have basically the same wear-resistant life, the thickness of the wear layer tends to be consistent. For the thicker bimetallic wear liner, the corresponding thickness of the base layer is increased, and the amount of high chromium cast iron is relatively small, which is conducive to reducing the material cost of the alloy.

A bimetallic wear liner, the preparation method is as follows:

1, Molten Metal Melting

The high chromium cast iron of the wear layer and the low alloy steel of the base layer are melted respectively by two intermediate frequency furnaces.

The pouring composition of molten iron of high chromium cast iron is (sampling in the ladle): 2.71% of C, 0.68% of Si, 0.92% of Mn, 26.7% of Cr, 0.51% of Mo, 0.32% of Ni, with the balance being Fe and inevitable impurities.

The pouring composition of molten steel of low alloy steel is (sampled in furnace): 0.22% of C, 0.38% of Si, 0.65% of Mn, 0.74% of Cr, with the balance being Fe and inevitable impurities.

The raw material for melting molten steel of low alloy steel into the furnace is high-quality scrap steel, and low phosphorus alloy should be used for alloying. After the molten steel is melted, deoxidizer is added first, then lime, bauxite and fluorite are added to quickly raise the temperature and melt the reducing slag. The deoxidizer adopts silicon-calcium-barium alloy, the addition amount of the deoxidizer is 0.45% of the mass fraction of molten steel in the furnace, the silicon-calcium-barium alloy components are 38.55%-42.69% of Si, 6.60%-7.26% of Ba, 18.17%-19.93% of Ca, and the balance is Fe and trace amounts of other impurities. Then alloying, and after the temperature is raised for 5 min, the high-temperature steel slag is mixed into the steel ladle. The mixing of steel slag increases the contact reaction interface between reducing slag and molten steel, and promotes the desulfurization and deoxidation reaction. In this example, the silicon-calcium-barium alloy components are 40.55% of Si, 6.78% of Ba, 19.31% of Ca, and the balance is Fe and trace amounts of other impurities.

The rare earth magnesium ferro-silicon alloy is pre-placed at the bottom of the steel ladle, and the rare earth magnesium ferro-silicon alloy is used to deoxidize the ladle. The chemical composition and mass fraction of the rare earth magnesium ferro-silicon alloy are: 6.17%-7.82% of RE (La+Ce), 7.05%-8.76% of Mg, 35.88%-43.14% of Si, ≤1.0% of Ti, ≤ of 1.0% Al, and the balance is Fe and trace amounts of other impurities. The size of the rare earth magnesium ferro-silicon alloy is 3-8 mm, and the addition amount is 0.30% of the mass fraction of the molten steel. After the molten steel in the steel ladle is stable, the slag is removed, and the slag collecting insulation agent is covered, and the ladle is transferred to the molding flask to stand for pouring. In this example, the size of the rare earth magnesium ferro-silicon alloy is 7 mm, and its chemical composition and mass fraction are: 6.87% of RE (La+Ce), 8.12% of Mg, 38.95% of Si, 0.54% of Ti, 0.19% of Al, and the balance is Fe and trace amounts of other impurities.

The melting raw materials of molten iron of high chromium cast iron into the furnace use scrap steel with low phosphorus content, carburizer, recycled charge, pig iron, high-carbon ferrochrome or industrial pure alloys. After completely melting, deoxidizer, lime, bauxite and fluorite are added to make reducing slag. Then alloying, high-temperature steel slag is mixed into the iron ladle after rapid heating. A gas permeable plug connected to inert gas is mounted at the bottom of the iron ladle. After iron tapping, argon or nitrogen inert gas is fed into the molten iron through the gas permeable plug to promote the stirring of the molten iron, enhance the contact between the molten iron and the reducing slag, and strengthen the desulfurization and deoxygenation reaction. At the same time as the gas is fed, the alloy wire is fed into the iron ladle for wire feeding treatment for modification and inoculation. After the treatment is completed, the gas is closed, the slag is removed, the slag collecting insulation agent is covered, and the ladle is transferred to the molding flask to stand for pouring.

The molten iron of high chromium cast iron is modified through a combination of the modification and inoculation treatment and reducing slag gas purging refining technology to improve the toughness of high chromium cast iron from by reducing inclusions and refining grains.

2, Modeling

The modeling is performed by the molding flask, as shown in FIG. 1 to FIG. 3. The molding flask includes the cope and the drag formed by combining, a cavity is between the cope and the drag, and a parting line between the cope and the drag is the bimetallic metallurgical composite interface, including a steel runner 1, a blind riser 2, an iron runner 3, an observation port 4, an overflow port 6, a slag collecting tank 5, a steel mesh 7 and an external chill 8. The steel runner 1 and the iron runner 3 are respectively independently arranged and distributed on two sides of the molding flask, the steel runner 1 is used for pouring molten steel of low alloy steel, the iron runner 3 is used for pouring molten iron of high chromium cast iron, and the runner thereof covers the lateral heat dissipation surface of the cavity. The inner gate of the steel runner 1 is arranged on the parting line of the drag, and the inner gate of the iron runner 3 is arranged on the parting line of the cope. The parting line of the cope is provided with the overflow port 6, and a plurality of the overflow ports 6 are respectively arranged on the opposite side of the inner gate of the iron runner 3 and the opposite side of the inner gate of the steel runner 1, the overflow ports 6 communicate with the cavity and the slag collecting tank 5, and the length of the slag collecting tank 5 covers the lateral heat dissipation surface of the cavity. The cavity is surrounded by two runners and two slag collecting tanks 5, and its lateral heat dissipation is restricted. The volume of the slag collecting tank 5 below the interface is larger than the volume of the molten steel in the steel runner 1 above the interface, or larger than the volume of the steel runner 1 above the interface, so as to ensure that the overflow port is still smooth after the molten steel of the low alloy steel is stopped pouring, and the interface is a lower plane of the overflow port 6. In order to conveniently observe the flow of molten steel of low alloy steel, the observation port 4 is arranged above the molding flask, on the opposite side of the steel runner 1, and directly above the slag collecting tank 5. The blind riser 2 is arranged inside the molding flask located above the cavity, which is used for the feeding of the molten iron of high chromium cast iron. The slag collecting tank 5 and the blind riser 2 are not exposed to the outside, so as to reduce the flow exchange with the outside air and avoid excessive oxidation of molten steel at the interface.

In the cavity, a steel mesh 7 is placed, and the steel mesh 7 is located 1-3 mm below the parting line. The void 9 having a larger size is machined in the steel mesh 7. An external chill 8 is arranged below the molding flask (the bottom surface of the drag), the upper surface shape of the external chill 8 is the same as the bottom surface shape of the base layer, the lower surface of the external chill 8 is a spherical surface, and the thickness dimension of the external chill 8 close to the steel runner 1 is larger than the dimensions of other edges, so as to strengthen the cooling of high-temperature molten steel and unfavorable heat dissipation places and ensure that the temperature of molten steel at the interface tends to be consistent. The void 9 in the steel mesh 7 should be arranged below the blind riser 2 to increase the direct feeding pressure of the low alloy steel. The mesh wire diameter and mesh wire arrangement of the steel mesh 7 are determined by the pouring temperature of molten steel of low alloy steel and the cooling capacity of molding sand. When simulating the interval time by computer software, the mesh wire diameter and mesh wire arrangement are simulated and designed at the same time, so that when the molten iron of high chromium cast iron is poured, the interface is at high temperature solid phase or low temperature solid-liquid two-phase temperature (high temperature solid phase temperature refers to high temperature zone of solid phase, low temperature solid-liquid two-phase temperature refers to the low temperature zone in the solid-liquid two-phase temperature range), that is, the temperature is set near the solidus line to facilitate the formation of bimetallic metallurgical bonding. At the interface of void 9, the low alloy steel is in the solid-liquid two-phase zone temperature, which provides a channel for the feeding of the molten steel of low alloy steel in the base layer.

S3, Pouring

In order to reduce the oxidation of molten steel and obtain a pure interface, organic film is laid on the molding flask before pouring, the iron runner 3, the observation port 4 and the ventilation hole (the ventilation hole is a conventional arrangement to ensure the smooth discharge of gas in the cavity) are covered. Firstly, molten steel of low alloy steel is poured from steel runner 1 at a pouring temperature of 1554° C. After the molten steel of low alloy steel is poured, its inner gate is blocked, and the cavity is completely isolated from the outside air. Before and after pouring, only the air in the cavity overflows, and no outside air enters. When pouring molten iron of high chromium cast iron, the refractory cotton is taken away, and the organic film covering the iron runner 3 is melted open with the poured molten iron.

In the process of molten steel pouring, the color of the overflow port 6 can be observed from the observation port 4. When the overflow port 6 is bright, the pouring is stopped, and the molten steel in the steel runner 1 continues to fill under the action of gravity. Or the observation port 4 is not provided, and the measure of controlling the pouring weight is adopted to control the molten steel filling of low alloy steel. The molten steel at the front end of the mold filling contacts with the air in the cavity, and there are oxidation slag inclusions, and it becomes low-temperature molten steel after flowing through the cavity. The molten steel flowing subsequently squeezes the front molten steel from the overflow port 6 into the slag collecting tank 5, and the molten steel in the molded cavity is high-temperature molten steel without oxidation or minimally oxidized, which is beneficial to obtaining a pure interface with good temperature uniformity.

The functions of the arrangement of the slag collecting tank 5: firstly, the low-temperature molten steel with oxide slag at the front end is collected, to obtain an ideal interface; secondly, the low-temperature molten iron with oxide slag at the front end is collected before the pouring of the high chromium cast iron, to strengthen the flow of molten iron at the interface; thirdly, the thickness of the base layer is ensured to be consistent, and the excess molten steel flows into the slag collecting tank 5; fourthly, heat dissipation around the plate is avoided, so that the heat dissipation of molten steel of low alloy steel is dominated by the upper and lower directions. After the low alloy steel is poured, molten steel is stored on three sides, a molten steel pouring runner and two slag collecting tanks 5, and the other side is a hollow molten iron runner that is closed to the outside, and the heat dissipation thermal resistance of the four sides is greatly increased. The above function of the slag collecting tank 5 makes the actual conditions and the simulated boundary conditions tend to be consistent, thus ensuring the correct interval time and obtaining an ideal metallurgical bonding.

Before the molten iron of high chromium cast iron is poured, the molten steel of low alloy steel solidifies in both directions, the external chill 8 at the bottom dissipates heat downward, and the steel mesh 7 at the interface is equivalent to the internal chill 10, which quickly cools the molten steel. Since the cavity is isolated from the outside and there is no low-temperature gas flow, when the steel mesh 7 is heated to a high temperature by molten steel, the temperature difference between the two decreases, and the temperature drop of the interface gradually decreases, mainly through downward heat dissipation. After the process interval time is reached, molten iron of high chromium cast iron is poured from iron runner 3 at a pouring temperature of 1487° C. At this time, the interface of the steel mesh 7 is arranged to be high-temperature solid state or low-temperature solid-liquid two phases, that is, the temperature is near the solidus temperature, and its function is equivalent to placing a high-temperature partition plate in the cavity to isolate the molten iron from mixing with the molten steel in the base layer. At the void 9 of the steel mesh 7, the interface is a low-temperature liquid void 9, which becomes a feeding channel of low alloy steel after molten iron is poured. Even at the temperature of the solid-liquid two-phase zone, the high-temperature soft shell layer of its solidified crust has no strength and is destroyed under the pressure of molten iron, forming a feeding channel of low alloy steel. The blind riser 2 is located above the void 9, which can increase the vertical pressure of the feeding of the low alloy steel. When the molten iron self-feeding channel enters the solidified shrinkage cavity of the molten steel in the base layer, it will no longer flow in a static state, the serious over-melting with the molten steel will not occur, and the composition of the high chromium cast iron in the wear-resistant layer will not be affected. After the high chromium cast iron is poured, the organic film is removed, and the blind riser 2 is communicated with the outside atmosphere through the ventilation hole, and the atmospheric pressure is used to increase the feeding pressure.

The molten iron at the front end of the molten iron of high chromium cast iron pouring flows through the interface, and the oxidized slag inclusions on the interface are brought into the slag collecting tank 5 from the overflow port 6, thus playing the role of purifying the interface. Additionally, during the molten iron of high chromium cast iron filling process, the molten iron flows at the interface, and even if the oxide slag on the interface does not all flow into the slag collecting tank 5, it will be wrapped up and float into the blind riser 2, so as to achieve the objective of purifying the interface. Furthermore, the flow of molten iron contributes to the uniform temperature of the interface, which provides convenience for the metallurgical bonding of the whole interface. Finally, a bimetallic liner with no shrinkage in the base layer and a metallurgical composite at the interface is formed.

After mold opening, the small piece of scrap steel in the steel runner 1 is returned to the furnace to melt the low alloy steel, and the returned materials of the blind riser 2, the slag collecting tank 5 and the iron runner 3 can be directly returned to the furnace for the melting of molten iron of high chromium cast iron. There is no waste or unrecyclable situation.

4, Heat Treatment

The cleaned bimetallic wear liner is heated to 1080° C. in the furnace and held for 60 min to achieve high-temperature homogenization and reduce casting segregation. Then, the furnace is cooled to 1000° C., and held for 80 min, and then removed from the furnace, stably suspended, the high chromium cast iron side of the liner is spray quenched, with the cooling rate of the spray quenching controlled at 25-32° C./s. The low alloy steel side is naturally cooled, which is equivalent to normalization. When the surface temperature of the low alloy steel side is 250° C., the liner is immediately sent to a heat treatment furnace at 250° C. and held for 5 h, followed by air cooling to room temperature after removal from the furnace, thereby obtaining a bimetallic wear liner.

Example 2

This example applies to producing a bimetallic wear liner with a base layer thickness of 15-30 mm, where the base layer is thinner relative to that obtained in Example 1.

The difference between the preparation method and Example 1 is in the chill, as follows:

1, Molten Metal Melting

The pouring composition of molten iron of high chromium cast iron is (sampling in the ladle): 2.77% of C, 0.41% of Si, 1.18% of Mn, 25.5% of Cr, 0.56% of Mo, 0.22% of Ni, with the balance being Fe and inevitable impurities.

The pouring composition of molten steel of low alloy steel is (sampled in furnace): 0.25% of C, 0.54% of Si, 0.73% of Mn, 0.47% of Cr, with the balance being Fe and inevitable impurities.

2, Modeling

In this example, as shown in FIG. 4, the external chill 8 in Example 1 is not used, and the internal chill 10 is used instead of the external chill 8. The internal chill 10 has a column-base structure, and the upper part is a small-diameter column body and the lower part is a large-diameter base. The upper column end is provided with a groove or a cross groove for supporting the steel mesh 7, and the large-diameter base at the lower end can stably support the steel mesh 7 to avoid scouring and tilting of molten steel, and the structure is also suitable for bidirectional solidification of low alloy steel.

3, Pouring

The molten steel of low alloy steel is poured from the steel runner 1 at a pouring temperature of 1548° C. After the process interval time is reached, molten iron of high chromium cast iron is poured from iron runner 3 at a pouring temperature of 1498° C.

4, Heat Treatment

The cleaned bimetallic wear liner is heated to 1050° C. in the furnace and held for 80 min to achieve high-temperature homogenization and reduce casting segregation. Then, the furnace is cooled to 980° C., and held for 90 min, and then removed from the furnace, stably suspended, the high chromium cast iron side of the bimetallic wear liner is spray quenched, with the cooling rate of the spray quenching controlled at 27-32° C./s. The low alloy steel side is naturally cooled, which is equivalent to normalization. When the surface temperature of the low alloy steel side is 200° C., the bimetallic wear liner is immediately sent to a heat treatment furnace at 200° C. and held for 8 h, followed by air cooling to room temperature after removal from the furnace, thereby obtaining a bimetallic wear liner.

Example 3

This example applies to producing a bimetallic wear liner with a base layer thickness of less than 15 mm, where the base layer is thinner relative to that obtained in Example 2.

The difference between the preparation method and Example 1 is that the chill is not used, as follows:

1, Molten Metal Melting

The pouring composition of molten iron of high chromium cast iron is (sampling in the ladle): 2.62% of C, 0.91% of Si, 0.64% of Mn, 26.7% of Cr, 0.42% of Mo, 0.37% of Ni, with the balance being Fe and inevitable impurities.

The pouring composition of molten steel of low alloy steel is (sampled in furnace): 0.27% of C, 0.42% of Si, 0.69% of Mn, 0.42% of Cr, with the balance being Fe and inevitable impurities.

2, Modeling

In this example, the chill is not used, and in the cavity structure, the external chill 8 is removed on the basis of Example 1. The steel mesh 7 is supported by multiple mesh wires. In order to avoid scouring and tilting of molten steel, the support wire can be inserted into the sand mold at the bottom of the cavity. Because the thickness of the base layer is thinner, the molten steel is basically mushy solidification, and the feeding problem of low alloy steel is not considered. The void 9 is not arranged on the steel mesh 7.

3, Pouring

The molten steel of low alloy steel is poured from the steel runner 1 at a pouring temperature of 1541° C. After the process interval time is reached, molten iron of high chromium cast iron is poured from iron runner 3 at a pouring temperature of 1492° C.

4, Heat Treatment

The cleaned bimetallic wear liner is heated to 1065° C. in the furnace and held for 70 min to achieve high-temperature homogenization and reduce casting segregation. Then, the furnace is cooled to 990° C., and held for 85 min, and then removed from the furnace, stably suspended, the high chromium cast iron side of the liner is spray quenched, with the cooling rate of the spray quenching controlled at 26-30° C./s. The low alloy steel side is naturally cooled, which is equivalent to normalization. When the surface temperature of the low alloy steel side is 230° C., the liner is immediately sent to a heat treatment furnace at 230° C. and held for 6.5 h, followed by air cooling to room temperature after removal from the furnace, thereby obtaining a bimetallic wear liner.

Experimental Testing

1. Mechanical property testing is performed on the bimetallic wear liner prepared in Examples 1 to 3. The test results are shown in Table 1.

TABLE 1
Mechanical property testing of bimetallic wear liner

Mechanical Properties

High chromium cast iron

Low alloy steel

		Impact	Tensile	Extension	Reduction
	Hardness	toughness	Strength	rate	of Area
	(HRC)	(J/cm2)	(MPa)	(%)	(%)

Example 1	62	3.6	965	20	27
Example 2	64	3.5	1020	19	26
Example 3	63	2.9	1040	19	25

As shown in Table 1, the mechanical properties of each wear liner are excellent and satisfy the usage standards for crusher liners.

2. The morphology and impact abrasive wear test and crusher trial analysis are performed on the bimetallic wear liner prepared in Example 3. The morphology results are shown in FIG. 5 and FIG. 6.

As shown in FIG. 5, a bimetallic liner with a martensite+carbide+retained austenite structure is successfully synthesized. As shown in FIG. 6, a bimetallic liner with a purified interface is obtained.

The impact abrasion test adopts an impact frequency of 100 cycles/min, a specimen rotation speed of 190 r/min, a test duration of 2 h, quartz sand as the abrasive material, an abrasive particle size of 20-40 mesh, and an abrasive flow rate of 12 kg/h. The results are shown in Table 2.

TABLE 2
Impact abrasion wear testing of bimetallic wear liner

	Impact	Before	After	Wear	Wear rate
	energy	testing	testing	amount	(g/10,000
Sample	(J)	(g)	(g)	(g)	cycles)

Example 3	3	22.0030	21.6657	0.3373	0.2810

As shown in Table 2, the bimetallic liner exhibits excellent product performance. Therefore, the present disclosure adopts the aforementioned bimetallic wear liner and its preparation method. The molten steel in a slag collecting tank is used to avoid heat dissipation around a base layer, and the molten steel in the base layer undergoes bidirectional heat dissipation. The interface retains local high temperature as a feeding channel of the base steel. In the pouring process, the cavity isolates air, to avoid oxidation, and purify the interface, and a metallurgical composite is obtained.

Finally, it should be noted that the above embodiments are merely used for describing the technical solutions of the present disclosure, rather than limiting the same. Although the present disclosure has been described in detail with reference to the preferred examples, those of ordinary skill in the art should understand that the technical solutions of the present disclosure may still be modified or equivalently replaced. However, these modifications or substitutions should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present disclosure.